Using magnetic particles as seeds for delivering drugs and therapy to targeted areas such as brain tumors and blood clots has been pursued for several decades. One area of research is to magnetically maneuver catheters through the vasculature for both diagnosis and delivery of therapy, and another is to magnetically manipulate small volumes of magnetic particles or powder after injection into the blood stream. This technique was to be used to induce thrombosis of intracranial aneurysms, and for the precise placement of ferromagnetic contrast agents for x-ray imaging. Other medical applications (such as urological, pulmonary, and orthopedic uses of the magnetic manipulation of magnetic particles and catheters) have been disclosed in the art.
Industrial applications of manipulating magnetic particles include magnetic separations and magnetic conveyer systems. The principle of magnetic control in either medical or industrial systems is to generate enough magnetic forces to move the magnetic parts or particles in the desired direction. Magnetic forces are proportional to the product of the magnetic field and its gradient. Therefore, generation and control of magnetic fields and its gradients are the main focus of a magnetic manipulation system. The magnetic particles or the tip of a catheter can be either soft magnetic (ferromagnetic) materials or hard ferromagnets such as NdFeB. For medical applications, the key issue is how to move the magnetic particles in a precise trajectory through human tissues, including blood vessels.
Currently, there are two methods of producing magnetic fields and field gradients for manipulating the magnetic particles in human tissue. The first method is to use permanent magnets and the second method is to use electromagnets (either conventional copper coil at room temperature or superconducting coil at liquid helium temperature). However, both methods have serious drawbacks in the amount of heat produced or in the size of the magnetic field produced by the magnets.